1. Field of the Invention
The present invention relates to an image scanning apparatus and an image scanning method, and more particularly to an image scanning apparatus and an image scanning method scanning high-quality images, properly inhibiting halation.
2. Discussion of the Background
In image scanning apparatuses of scanning apparatuses, copiers, complex machines, etc., linear light sources capable of emitting continuous linear reading light to an original to be scanned such as Xe lamps and cold-cathode tube lamps have conventionally been used.
However, these light sources largely vary in light quantity as time passes and have short lives, and are difficult to maintain and expensive.
When the scanning light is emitted to the original to scan while the original is floating from a transparent original table, halation occurs, i.e., the original image density increases (images scanned become white).
Recently, lower-cost, longer-life and easier-controlled LEDs (Light Emitting Diodes) have been used as light sources for scanning images.
When the LED emitting point-like light is used as a light source, a light source substrate on which the LEDs are arrayed in the scanning direction is typically used.
Different from the conventional linear light sources such as Xe lamps, the LED-arrayed light source has strong light intensity at positions corresponding to array pitches of the LEDs and abnormal images having dotted blanks in a specific line are produced as FIG. 12 shows. Such halation is likely to occur when the center of a book placed on a contact glass, which is floating from the glass is scanned. In addition, glossy originals tends to occur halation more. Namely, this is because regular-reflected light at a curved part enters a light axis collecting scanning light comes to have strong light intensity. Japanese published unexamined application No. 2007-212949 discloses a method of locating a light-emitting element emitting light through a transparent material to an original such that a part of the light causing abnormal images is totally reflected on the transparent material or a shade member inhibiting the light from reaching the original to prevent halation.
However, because a part the scanning light is totally reflected on the transparent material or shaded with a shade member to prevent halation, the light quantity of the scanning light lowers, resulting in deterioration of reading efficiency, or the extra shade member increases the cost.
Because of these reasons, a need exists for an image scanning apparatus and an image scanning method capable of forming high-quality scanned images at low cost, preventing halation images having dotted blanks when using a light source in which dotted light-emitting elements are linearly arrayed.